Image sharpness of photographic light-sensitive materials generally decreases with increasing thickness of an emulsion layer due to light scattering of the silver halide grains. In particular, in multilayer color photographic materials containing a red-sensitive emulsion layer, a green-sensitive emulsion layer and a blue-sensitive emulsion layer, the reduction in image sharpness of lower emulsion layers is remarkably large due to the cumulative effect of light scattering in the multilayer structure.
In U.S. Pat. No. 4,439,520, there is described a color photographic light-sensitive material having improved sharpness, sensitivity and graininess using tabular silver halide grains having a thickness of less than 0.3 micron, a diameter of at least 0.6 micron and a ratio of diameter/thickness, i.e., an aspect ratio of not less than 8 in at least one of the green-sensitive emulsion layer and the red-sensitive emulsion layer.
Such a method of utilizing tabular silver halide grains in a color photographic light-sensitive material is excellent since improvement in spectral sensitization efficiency, omission of yellow filter layer and improvement in sharpness can be realized.
However, tabular silver halide grains which are prepared by known methods have a broad grain size distribution and thus it is very difficult to expect a steep gradient (so-called "high gamma") of the characteristic curve. Further, the graininess in the low density region of negative images is inferior to that of emulsions consisting of non-tabular silver halide grains having a narrow grain size distribution.
The above-described defects are more conspicuous when such tabular grains are subjected to color reversal processing which basically comprises the sequential steps of black-and-white development (first development), reversal, color development, bleaching and fixing. More specifically, since tabular grains have a large ratio of surface area to volume, they are apt to be dissolved with a silver halide solvent contained in a first developing solution employed in the first development. In particular, when using tabular grains having a broad grain size distribution, grains having a smaller grain size are easily dissolved and disappear resulting in a decrease in image density after color development and in degradation of graininess due to a reduction in points for initiating color development, etc.
For the above reasons, it is very difficult to apply tabular silver halide grains to color photographic light-sensitive materials without an accompanying degradation of graininess.